Collagen is a major component of connective tissue in the body. Type I collagen is a major component of tendons, skin, bone and is responsible for transmitting force from muscle to bone. The various types of collagens share many structural features. Since Collagen type I is particularly well ordered, it is a good model system to study intermolecular packing in these materials. For a number of years we have used rat-tail tendon as a model system for studying this tissue. Using the BioCAT beamline, we were able to collect data from native and three heavy atom derivatives of Type I collagen. Using this data we were able to refine our 1-D structure and are now attempting to obtain a preliminary phasing towards solving a detailed 3-D fiber structure.